The present invention relates to built-in test (BIT), and in particular to BIT for a current sensing circuit.
Current sensing circuits typically employ a current transformer to monitor current in a system. The current in the system passes through the primary coil of the transformer, which generates a proportional current in the secondary coil of the transformer based upon the ratio of turns in each coil. This proportional current flows through a burden resistor in order to create a voltage that is measurable by a monitor circuit.
Current sensing circuits are tested to ensure proper functionality. In the past, this involved using separate circuitry to inject currents directly to the burden resistor in order to test the monitor circuit. This is not ideal in that it requires external circuitry, and does not test the current transformer itself.